The present invention relates to therapeutic and prophylactic devices, and more particularly to devices for applying compressive pressures against a patient's limb.
It is known that the velocity of blood flow in a patient's extremities, particularly the legs, markedly decreases during confinement of the patient. Such pooling or stasis of blood is particularly pronounced during surgery, immediately after surgery, and when the patient has been confined to bed for extended periods of time. It is also known that stasis of blood is a significant cause leading to the formation of thrombi in the patient's extremities, which may have a severe deleterious effect on the patient, including death. Additionally, in certain patients it is desirable to move fluid out of interstitial spaces in extremity tissues, in order to reduce swelling associated with edema in the extremities.
Devices have been disclosed in U.S. Pat. Nos. 4,013,069 and 4,030,488, incorporated herein by reference, which develop and apply the desired compressive pressures against the patient's limbs. Such devices comprise a pair of sleeves which envelop the patient's limbs, and a controller for supplying fluid pressure to the sleeves through conduits which are connected in fluid communication with chambers in the sleeve. During use of the device it is desirable to know the pressure in at least one chamber of the sleeve, but prior to the invention it was necessary to connect a pressure gauge directly to the chamber, thus requiring an extra conduit leading to the sleeve which resulted in extra cost and inconvenience in use.